JP2008016811A - Stripping method for photoresist - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stripping method for photoresist by which a photoresist used when ions are implanted by high implant dose can be easily stripped without leaving residue. <P>SOLUTION: This method includes a step for forming, on a specified material layer 21, a photoresist pattern which exposes the part where the ions are implanted, a step for ion-implanting impurity elements into the specified material layer 21 with the photoresist pattern as an ion implantation barrier, and a step for stripping the photoresist pattern by using plasma of a mixed gas containing at least a hydrocarbon-based gas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for stripping a photoresist used as a barrier for ion implantation at a high concentration.

  Of the semiconductor device manufacturing processes, in the ion implantation process, a photoresist is usually used as an ion implantation mask. For example, a photoresist is used as an ion implantation mask in a process of forming a dual poly gate or the like.

  1A to 1C are cross-sectional views illustrating a conventional method for forming a dual poly gate, showing the structure of an element at each stage of the forming process.

  FIG. 1A shows a stage in which an N-type impurity element is implanted into an NMOS region of a semiconductor substrate using a photoresist pattern. As shown in FIG. 1A, after an element isolation film 12 for isolating elements is formed on a semiconductor substrate 11 in which an NMOS region and a PMOS region are defined, a gate oxide film 13 is formed on the semiconductor substrate 11, A gate polysilicon layer 14 is formed on gate oxide film 13.

Subsequently, the NMOS region is exposed, and an N-type impurity element is implanted into the gate polysilicon layer 14 in the NMOS region by ion implantation (N ⁺ IMP) of the N-type impurity element using the first photoresist pattern 15 covering the PMOS region. Ion implantation is performed to form an N-type doped polysilicon layer 14A.

  FIG. 1B shows a stage in which a P-type impurity element is implanted into the PMOS region of the semiconductor substrate using a photoresist pattern. As shown in FIG. 1B, after the first photoresist pattern 15 is stripped, a photoresist is applied again, patterning is performed by exposure and development, the PMOS region is exposed, and a second photoresist pattern 16 covering the NMOS region is formed. Form.

Subsequently, a P-type impurity element is implanted into the gate polysilicon layer 14 in the PMOS region by ion implantation (P ⁺ IMP) of a P-type impurity element using the second photoresist pattern 16, thereby forming a P-type doped polysilicon. Layer 14B is formed.

FIG. 1C shows a stage in which gates are formed in the NMOS region and the PMOS region, respectively. After the second photoresist pattern 16 is stripped, a tungsten silicide layer is formed on the entire surface, and then, as shown in FIG. 1C, gate patterning is performed, and an N-type doped layer having a tungsten silicide layer 17 on the upper portion in the NMOS region. An N ⁺ poly gate 14C made of polysilicon is formed, and a P ⁺ poly gate 14D made of P-type doped polysilicon having a tungsten silicide layer 17 on top is formed in the PMOS region.

In the above-described conventional technology, in order to form a dual polygate composed of the N ⁺ polygate 14C and the P ⁺ polygate 14D, an N-type impurity element (for example, phosphorus) and a P-type are formed in the gate polysilicon layer 14 respectively. Ion implantation of an impurity element (for example, boron) is performed. At this time, the ion implantation amount is in the range of 1 × 10 ¹⁵ to 1 × 10 ¹⁶ ions / cm ² , and high-density ion implantation is performed.

In the prior art, a mixed gas of oxygen and nitrogen (O ₂ / N ₂ gas) is used to strip the first photoresist pattern 15 and the second photoresist pattern 16 after ion implantation.

However, in the case of the above conventional technique, the first photoresist pattern 15 and the second photoresist pattern 16 are remarkably cured by high-density ion implantation, so that the photoresist strip is not smoothly performed. For this reason, there is a problem that photoresist residues that have not been removed remain everywhere after stripping. Such a problem is that oxygen gas (O ₂ ) used in stripping reacts with impurity elements (As, P, B) present in the photoresist pattern, and oxides of the impurity elements (As ₂ O ₃ , This is because a film of P ₄ O ₆ , B ₂ O ₃ ) is formed and the film covers the surface of the photoresist pattern.

  Therefore, the photoresist residue left without being removed at the time of stripping causes abnormal oxidation of the tungsten silicide layer 17 formed in the subsequent process, and further, at the interface between the polygates 14C and 14D and the tungsten silicide layer 17. Since the bonding state is poor, there is a problem that after the patterning of the gate, it causes lifting or particle generation.

  In addition, when the doping level in ion implantation is high, the photoresist is difficult to remove, and thus there is a problem that the time required for removing the photoresist becomes long and mass productivity is reduced.

  FIG. 1D is a view showing a residue after removing a photoresist by a conventional technique, and shows a scanning electron microscope (SEM) photograph.

  The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to easily strip a photoresist used for high concentration ion implantation without leaving a residue. It is to provide a method for stripping a photoresist.

In order to achieve the above object, a photoresist strip method according to the present invention includes a step of forming a photoresist pattern exposing a portion into which ions are implanted on a predetermined material layer, and ionizing the photoresist pattern. The implantation barrier includes ion implantation of an impurity element into the predetermined material layer, and stripping the photoresist pattern using plasma of a mixed gas containing at least a hydrocarbon-based gas. According to another aspect of the present invention, there is provided a photoresist strip method comprising: forming a first photoresist pattern in which a part of the polysilicon layer is exposed on a polysilicon layer; and As an ion implantation barrier, a first impurity element is ion-implanted into the polysilicon layer. A step of stripping the first photoresist pattern using plasma of a mixed gas containing at least N ₂ H ₂ gas; and the first impurity element is ion-implanted on the polysilicon layer. Forming a second photoresist pattern that exposes the remaining region excluding the region; implanting a second impurity element into the polysilicon layer using the second photoresist pattern as an ion implantation barrier; And stripping the second photoresist pattern using a mixed gas plasma containing at least N ₂ H ₂ gas.

Hereinafter, the most preferred embodiment of the present invention will be described with reference to the accompanying drawings.
(First embodiment)
2A to 2D are views for explaining the photoresist stripping method according to the first embodiment of the present invention, and are sectional views showing a structure including a substrate portion at each stage of the process using the photoresist. It is. The following photoresist strip method relates to a strip method after forming a dual poly gate as an example.

  FIG. 2A shows a step of implanting an N-type impurity element into the NMOS region of the semiconductor substrate using a photoresist pattern. As shown in FIG. 2A, an element isolation film 22 for separating the NMOS region and the PMOS region is formed on the semiconductor substrate 21 in which the NMOS region and the PMOS region are defined.

  Thereafter, a gate oxide film 23 is formed on the semiconductor substrate 21, and a gate polysilicon layer 24 is formed on the gate oxide film 23.

  Subsequently, a photoresist is applied onto the gate polysilicon layer 24, and patterning is performed by exposure and development to expose the NMOS region and form a first photoresist pattern 25 that covers the PMOS region.

Next, ion implantation (N ⁺ IMP) of an N-type impurity element is performed using the first photoresist pattern 25, an N-type impurity element is implanted into the gate polysilicon layer 24 in the NMOS region, and N-type doped poly A silicon layer 24A is formed. The N-type impurity element is phosphorus (P) or arsenic (As), and the ion implantation amount is set to a very high level of about 1 × 10 ¹⁶ ions / cm ² and the ion implantation energy is set to a low level.

After ion implantation (N ⁺ IMP) of an N-type impurity element, an N-type doped polysilicon layer 24A is formed on the NMOS region, and a gate polysilicon layer 24 in a state where ions are not implanted remains on the PMOS region. . Hereinafter, the N-type doped polysilicon layer 24A is abbreviated as “N ⁺ polysilicon layer 24A”.

FIG. 2B shows the step of stripping the photoresist over the PMOS region. As shown in FIG. 2B, the first photoresist pattern 25 shown in FIG. 2A is stripped. At this time, the strip of the first photoresist pattern 25 is mainly a mixed gas of oxygen gas (hereinafter sometimes referred to as “O ₂ ”) and nitrogen gas (hereinafter sometimes referred to as “N ₂ ”). (O ₂ / N ₂ ) may be further described as a hydrocarbon-based gas (CH ₄ gas (hereinafter sometimes referred to as “CH ₄ ”) or C ₂ H ₄ gas (hereinafter referred to as “C ₂ H ₄ ”). A plasma using a mixed gas added with a) is used as a source gas. That is, the gas used for stripping the first photoresist pattern 25 is mainly a mixed gas of O ₂ / N ₂ / CH ₄ , O ₂ / N ₂ / C ₂ H ₄ , and in addition, CH ₄ gas or C _{4 2} H ₄ gas is used alone.

Here, the hydrocarbon-based gas such as methane (CH ₄ ) or ethylene (C ₂ H ₄ ) is a gas for removing the impurity element contained in the first photoresist pattern 25 to the outside. Since these CH ₄ gases have a boiling point of −163 ° C. and C ₂ H ₄ gas has a boiling point of −103 ° C., they easily react with impurity elements in the first photoresist pattern 25 in a gaseous state at a low temperature. The impurity element can be formed and the impurity element can be removed from the resist layer in the form of a hydride.

When stripping the first photoresist pattern 25, plasma using the mixed gas as a source gas is used. As an energy source for generating a plasma, a microwave and an RF bias are simultaneously used (that is, combined). In addition, as described above, the plasma source gas is a gas containing at least a hydrocarbon-based gas. For example, when CH ₄ gas or C ₂ H ₄ gas is used alone, an appropriate amount of O ₂ gas is added to these gases. It may be used as a mixture. That is, gases of CH ₄ , C ₂ H ₄ , CH ₄ / O ₂ , and C ₂ H ₄ / O ₂ are used. Here, in the case of mixing O ₂ gas, the mixing ratio of CH ₄ : O ₂ or C ₂ H ₄ : O ₂ is 4 to 10: 1 by volume ratio, and hydrocarbons are compared with O ₂ gas. Increase the amount of system gas.

The strip of the first photoresist pattern 25 under the above-described conditions is performed by dividing one strip into three times in the order of the next first step, second step and third step. Hereinafter, a case where a mixed gas of CH ₄ and O ₂ is used will be described.

In the first step, processing is performed at a low temperature (100 to 160 ° C.) using plasma using a mixed gas of CH ₄ gas and O ₂ gas as a source gas. In the second step, processing is performed at a higher temperature (200 to 250 ° C.) than in the first step using plasma using a mixed gas of CH ₄ gas and O ₂ gas as a source gas. In the final third step, processing is performed using plasma using CH ₄ gas alone as a source gas.

As described above, in the first step, plasma using a mixed gas of CH ₄ gas and O ₂ gas as a source gas at a low temperature in the range of 100 to 160 ° C. is used. Here, the CH ₄ plasma serves as a forming gas for releasing an impurity element (for example, arsenic (As)). That is, the arsenic (As) implanted into the first photoresist pattern 25 during ion implantation serves to remove the arsenic (As) from the inside of the first photoresist pattern 25 to the outside. The O ₂ plasma plays a role of stripping the first photoresist pattern 25.

The reason why the first step is performed at a low temperature is that O ₂ plasma is prevented from reacting with arsenic (As) to generate As ₂ O _{3, and} arsenic (As) is likely to be detached by CH ₄ plasma. It is for doing so. That is, in the low temperature range of 100 to 160 ° C., than the generation of _As 2 _{O 3} by the _{O 2} plasma, separation of arsenic (As) due to CH ₄ plasma is generated in advance, then, first by _{O 2} plasma Photoresist pattern 25 is stripped.

  Next, the detachment process of arsenic (As) remaining in the first photoresist pattern 25 will be described based on a chemical reaction formula.

When a mixed gas of CH ₄ gas and O ₂ gas is used as a plasma source, when electrical energy (microwave and RF bias) is applied simultaneously, the CH ₄ gas and O ₂ gas are in a plasma state due to collision with accelerated electrons. It is activated by (positive ion, negative ion, electron, radical, etc.). Ions, radicals, etc. generated by converting the CH ₄ / O ₂ gas into plasma are involved in the stripping of the photoresist and the removal of impurity elements. In the first to third steps, a microwave (MW) and an RF bias are used simultaneously for plasma generation. Therefore, during the processing in the first step to the third step, the CH ₄ gas becomes CH ₄ -MW plasma and CH ₄ -RF bias plasma and plays its role, and O ₂ is O ₂ -MW plasma and It becomes O ₂ -RF bias plasma and plays its role.

Hereinafter, the arsenic (As) elimination process will be described in detail based on the chemical reaction formula.
Chemical reaction 1:
2As + 6H * → As ₂ H ₆ (gas)
As + O * / O ₃ → As ₂ O ₃ (solid)
As ₂ O ₃ + 12H * → As ₂ H ₆ (gas) + 3H ₂ O (gas)
In the chemical reaction 1, As is arsenic remaining in the first photoresist pattern 25, and H * is a hydrogen radical contained in the CH ₄ plasma. O * / O ₃ is oxygen radicals / ozone contained in the O ₂ plasma.

According to the chemical reaction 1, As remaining in the first photoresist pattern 25 reacts with H * and is vaporized as As ₂ H ₆ (gas).

In addition, As remaining in the first photoresist pattern 25 reacts with O * and O ₃ contained in the O ₂ plasma to produce solid As ₂ O ₃ . Even when solid As ₂ O ₃ is produced, As ₂ O ₃ reacts with H * and vaporizes as As ₂ H ₆ (gas). Here, 3H ₂ O which is a reaction byproduct of As ₂ O ₃ and H * is volatilized as a gas.

In the method of strip photoresist using only O ₂ gas as in the conventional art, As present inside the photoresist to produce a solid As ₂ O ₃ reacts with O ₂ gas reaction, ie Then, the generation of the oxide film by the impurity element occurs prior to the strip of the photoresist pattern by the O ₂ gas. Therefore, the strip of the photoresist pattern by O ₂ gas is inhibited by the As ₂ O ₃ film.

In the case of the embodiment according to the present invention, when the first step is performed, plasma using a mixed gas of CH ₄ gas and O ₂ gas as a source is used, so that it remains inside the first photoresist pattern 25. Arsenic (As) that is present can be released to the outside, thereby preventing the formation of a solid As ₂ O ₃ film on the surface of the first photoresist pattern 25.

Next, a second step is performed following the first step. In this second step, plasma is set to a higher temperature condition (200 to 250 ° C.) than in the first step, and the same mixed gas (mixed gas of CH ₄ gas and O ₂ gas) as in the first step is used as the source gas. Is used. Here, the reason why the temperature condition of the second step is set higher than that of the first step is that the strip speed of the first photoresist pattern 25 can be further increased at a high temperature (200 to 250 ° C.).

Accordingly, the detachment of the impurity element arsenic (As) proceeds preferentially over the strip action of the first photoresist pattern 25 during the first step, and arsenic (As) has already been achieved during the second step. Therefore, stripping of the first photoresist pattern 25 by O ₂ gas plasma mainly proceeds. If stripping of the photoresist is performed at a high temperature from the beginning, problems such as popping occur and the strip rate decreases. Therefore, it is advantageous from the viewpoint of improving the strip rate of the photoresist to perform the second step at a higher temperature after performing the first step at a low temperature.

Finally, the third step is performed following the second step. In this third step, arsenic (As) that may remain in the strip by-product generated up to the second step is removed by using plasma using CH ₄ gas alone as a source gas. . That is, the third step is a process of removing the impurity element remaining in the strip byproduct remaining after the first photoresist pattern 25 is stripped.

  Through the series of first to third steps as described above, the first photoresist pattern 25 is completely removed from the substrate surface without the photoresist remaining.

On the other hand, when phosphorus (P) is implanted into the N ⁺ polysilicon layer 24A, phosphorus (P) is released by the following chemical reaction 2.
Chemical reaction 2:
P + 3H * → PH ₃ (gas)
P + O * / O ₃ → P ₄ O ₆ (solid) or P ₄ O ₁₀ (solid)
P ₄ O ₆ + 24H * → 4PH ₃ (gas) + 6H ₂ O (gas)
P ₄ O ₁₀ + 32H * → 4PH ₃ (gas) + 10H ₂ O (gas)
FIG. 2C shows a step of implanting a P-type impurity element into the PMOS region of the semiconductor substrate using a photoresist pattern. After the first photoresist pattern 25 is stripped by a series of methods as described above, as shown in FIG. 2C, a photoresist is applied again, and exposure and development are performed to form a second photoresist pattern 26.

That is, in a state where the N ⁺ polysilicon layer 24A and the gate polysilicon layer 24 coexist, a photoresist is applied to the entire surface, followed by patterning by exposure and development, exposing the PMOS region, and covering the NMOS region. A resist pattern 26 is formed.

Next, ion implantation (P ⁺ IMP) of a P-type impurity element is performed using the second photoresist pattern 26, and a P-type impurity element is implanted into the gate polysilicon layer 24 in the PMOS region. Layer 24B is formed. At this time, for example, boron (B) is used as the P-type impurity element, the ion implantation amount is set to a very high level of about 1 × 10 ¹⁶ ions / cm ² , and the ion implantation energy is set to a low level.

FIG. 2D shows the step of stripping the photoresist over the NMOS region. As shown in FIG. 2D, the second photoresist pattern 26 shown in FIG. 2C is stripped. At this time, the strip of the second photoresist pattern 26 includes a mixed gas (O ₂ / N ₂ ) of oxygen (O ₂ ) and nitrogen (N ₂ ), and a hydrocarbon system such as CH ₄ and C ₂ H _4. Plasma using a mixed gas to which a gas is added as a source gas is used. That is, the gas used for the strip of the second photoresist pattern 26 is mainly a mixed gas of O ₂ / N ₂ / CH ₄ or O ₂ / N ₂ / C ₂ H ₄ , in addition to CH ₄ gas, C _{4 2} H ₄ gas is used alone.

Here, the hydrocarbon gas such as CH ₄ gas or C ₂ H ₄ gas is a gas for removing the impurity element contained in the second photoresist pattern 26 to the outside. Among these gases, CH ₄ gas has a boiling point of −163 ° C., and C ₂ H ₄ gas has a boiling point of −103 ° C., and thus reacts easily with the impurity element in the second photoresist pattern 26 in a gas state. It is possible to form a hydride and remove the impurity element from the resist layer in the form of a hydride.

When stripping the second photoresist pattern 26, a microwave and an RF bias are simultaneously used as electrical energy for plasma generation. Further, as described above, when a gas containing at least a hydrocarbon-based gas, for example, CH ₄ gas or C ₂ H ₄ gas is used alone as the plasma source gas, an appropriate amount of O ₂ gas is mixed with those gases. May be used. That is, gases of CH ₄ , C ₂ H ₄ , CH ₄ / O ₂ , and C ₂ H ₄ / O ₂ are used. Here, in the case of mixing O ₂ gas, the mixing ratio of CH ₄ : O ₂ or C ₂ H ₄ : O ₂ is 4 to 10: 1 by volume ratio, and hydrocarbons are compared with O ₂ gas. Increase the flow rate of the system gas.

Stripping of the second photoresist pattern 26 under the above conditions is performed in three steps in the order of the following first step, second step, and third step. Hereinafter, a case where a mixed gas of CH ₄ and O ₂ is used will be described.

In the first step, processing is performed at a low temperature (100 to 160 ° C.) using plasma using a mixed gas of CH ₄ gas and O ₂ gas as a source gas. In the second step, processing is performed at a higher temperature (200 to 250 ° C.) than in the first step using plasma using a mixed gas of CH ₄ gas and O ₂ gas as a source gas. In the final third step, processing is performed using plasma using CH ₄ gas alone as a source gas.

As described above, in the first step, plasma using a mixed gas of CH ₄ gas and O ₂ gas as a source gas at a low temperature in the range of 100 to 160 ° C. is used. Here, the CH ₄ plasma serves as a forming gas for separating impurity elements (for example, boron (B)). That is, the boron (B) implanted into the second photoresist pattern 26 at the time of ion implantation is removed from the inside of the second photoresist pattern 26 to the outside. The O ₂ plasma serves to strip the second photoresist pattern 26.

The reason why the first step is performed at a low temperature is that the O ₂ plasma reacts with boron (B) to suppress the formation of B ₂ O ₃ , and the separation of boron (B) by the CH ₄ plasma is likely to occur. It is for doing so. That is, in the low temperature range of 100 to 160 ° C., than the generation of _B 2 _{O 3} by the _{O 2} plasma, generated in advance is separation of boron (B) according to CH ₄ plasma, then, the second by _{O 2} plasma Photoresist pattern 26 is stripped.

  Next, the process of removing boron (B) remaining in the second photoresist pattern 26 will be described based on the chemical reaction formula.

When a mixed gas of CH ₄ gas and O ₂ gas is used as a plasma source, when microwave and RF bias are simultaneously applied as electric energy, CH ₄ gas and O ₂ gas are in a plasma state due to collision with accelerated electrons. (Positive ions, negative ions, electrons, radicals, etc.) are activated. Ions, radicals, etc. generated by converting the CH ₄ / O ₂ gas into plasma are involved in the stripping of the photoresist and the removal of impurity elements. In the first to third steps, a microwave (MW) and an RF bias are used simultaneously for plasma generation. Therefore, during the processing in the first step to the third step, the CH ₄ gas becomes CH ₄ -MW plasma and CH ₄ -RF bias plasma and plays its role, and O ₂ is O ₂ -MW plasma and It becomes O ₂ -RF bias plasma and plays its role.

Hereinafter, the process of removing boron (B) will be described in detail based on the chemical reaction formula.
Chemical reaction 3:
2B + 6H * → B ₂ H ₆ (gas)
B + O * / O ₃ → B ₂ O ₃ (solid)
B ₂ O ₃ + 12H * → B ₂ H ₆ (gas) + 3H ₂ O (gas)
In the chemical reaction 3, B is boron remaining inside the second photoresist pattern 26, and H * is a hydrogen radical contained in the CH ₄ plasma. O * / O ₃ is oxygen radicals / ozone contained in the O ₂ plasma.

According to the chemical reaction 3, boron (B) remaining inside the second photoresist pattern 26 reacts with H * and is vaporized as B ₂ H ₂ (gas).

Further, boron (B) remaining in the second photoresist pattern 26 reacts with O * and O ₃ contained in the O ₂ plasma to generate solid B ₂ O ₃ . Even if solid B ₂ O ₃ is produced, the produced B ₂ O ₃ reacts with H * and is vaporized as B ₂ H ₂ (gas). Here, 3H ₂ O which is a reaction byproduct of B ₂ O ₃ and H * is volatilized as a gas.

In the conventional method of stripping a photoresist using only O ₂ gas, boron (B) existing inside the photoresist reacts with O ₂ gas to generate solid B ₂ O ₃ . The reaction, that is, the formation of an oxide film by the impurity element, occurs prior to the strip of the photoresist pattern by O ₂ gas. Therefore, the strip of the photoresist pattern by O ₂ gas is inhibited by the B ₂ O ₃ film.

In the case of the embodiment according to the present invention, when the first step is performed, plasma using a mixed gas of CH ₄ gas and O ₂ gas as a source gas is used, so that it remains inside the second photoresist pattern 26. Boron (B) can be released to the outside, thereby preventing the formation of a solid B ₂ O ₃ film on the surface of the second photoresist pattern 26.

Next, a second step is performed following the first step. The second step is a plasma that uses a higher temperature condition (200 to 250 ° C.) than the first step and uses the same mixed gas (a mixed gas of CH ₄ gas and O ₂ gas) as that of the first step as a source gas. Is used. Here, the reason why the temperature condition of the second step is set higher than that of the first step is that the strip speed of the second photoresist pattern 26 can be further increased at a high temperature (200 to 250 ° C.).

Accordingly, in the first step, the removal of boron (B) of the impurity element preferentially proceeds over the strip action of the second photoresist pattern 26, and in the second step, boron (B ) Is removed, the strip of the second photoresist pattern 26 by the substantial O ₂ gas plasma proceeds mainly.

Finally, the third step is performed following the second step. In the third step, boron (B) that may remain in the strip by-product generated up to the second step is removed by using plasma using CH ₄ gas alone as a source gas. . That is, the third step is a process of removing boron (B), which is an impurity element remaining in the strip byproduct remaining after the second photoresist pattern 26 is stripped.

  Through the series of first to third steps as described above, the second photoresist pattern 26 is completely removed from the substrate surface without the photoresist remaining.

FIG. 3 is a diagram showing a photoresist strip process by a process using plasma of a CH ₄ / O ₂ mixed gas after boron is ion-implanted with a low level ion implantation energy and a high ion implantation amount.

As shown in FIG. 3, the simultaneous use of microwaves and RF bias for plasma generation, CH _{4 gas,} plays its role in a CH 4 -MW plasma and _CH 4 -RF bias plasma, _{O 2} The gas plays the role of O ₂ -MW plasma and O ₂ -RF bias plasma.

First, in strip processing, “B ₂ O ₃ and PR” coexist in the upper layer of the photoresist (PR), and only “PR” exists in the lower layer in contact with the gate polysilicon layer, “BxHyOz and PR” coexist in the intermediate layer between the upper layer and the lower layer. Here, BxHyOz of the hydride existing in the intermediate layer is generated by reacting hydrogen radicals with B ₂ O _{3 in the} plasma, and is changed into a gas state by H * like B ₂ O ₃ , It is removed as a gas.

As described above, a photoresist (PR) layer is present in various states, _B 2 _{O 3} and PR of the upper layer _is stripped by CH 4 -MW plasma and _CH 4 -RF bias plasma, an intermediate layer BxHyOz And PR are stripped by CH ₄ -MW plasma and O ₂ -RF bias plasma, and PR in the lower layer is stripped by CH ₄ -plasma and O ₂ / N ₂ -MW plasma or O ₂ -MW plasma. Here, B ₂ O ₃ and BxHyOz in each layer are vaporized as B ₂ H ₆ by the principle of the chemical reaction 3 described above.

The lower layer where only PR is present is stripped by CH ₄ -plasma, O ₂ / N ₂ -MW plasma, and O ₂ -MW plasma. However, since PR is usually a polymer of “C” and “H”, it is stripped by reacting with O ₂ and volatilizing as a gas of CO ₂ and H ₂ O.

Even when stripping is performed using plasma using a mixed gas of C ₂ H ₄ gas and O ₂ gas as a source gas, the stripping is performed by the mechanism shown in FIG.

As shown in FIG. 3, in the embodiment according to the present invention, hydrocarbon gas (C ₂ H ₄ , CH ₄₎ is used so that volatile hydride can be generated and photoresist strip can be easily performed. ).

According to the method of the first embodiment described above, since a hydrocarbon gas such as C ₂ H ₄ or CH ₄ is used for stripping a photoresist used as a barrier during ion implantation, the impurity element The generation of the oxide film due to the etching can be prevented, and the impurity element inside the photoresist layer can be easily removed. For this reason, the photoresist can be stripped without leaving a residue of the photoresist.

Since oxide films of impurity elements such as As ₂ O ₃ , P ₄ O ₆ , P ₄ O ₁₀ , and B ₂ O ₃ are water-soluble, before the strip processing of the photoresist (especially before the first step), A pretreatment for removing the oxide film of the impurity element is performed using deionized water (hereinafter, also referred to as “DI”) at an appropriate temperature. This pretreatment is called “deionized water rinse” and is preferably performed by a method of immersing an object to be treated in deionized water (H ₂ O) containing ozone (O ₃ ). Here, the deionized water containing ozone preferably has a solution temperature range of 25 to 80 ° C. and an ozone concentration of 0 to 1000 ppm, and the deionized water containing ozone is simply expressed as “H ₂ O”. can do.

In the rinsing process using deionized water, the object to be processed is exposed to the atmosphere when the impurity element is ion-implanted and then moved to a photoresist strip apparatus, and As ₂ O is reacted by the reaction between oxygen in the atmosphere and the impurity element. _Since an oxide film of an impurity element such as ₃ , P ₄ O ₆ , P ₄ O ₁₀ , or B ₂ O ₃ is generated, it is applied to remove the oxide film. By rinsing with deionized water, the surface layer portion of the photoresist layer into which the impurity element is ion-implanted is softened, and the oxide film of the impurity element is removed.

The pre-treatment using deionized water described above further facilitates the subsequent stripping of the photoresist.
(Second Embodiment)
4A to 4E are views for explaining a photoresist stripping method according to the second embodiment of the present invention, and are sectional views showing a structure including a substrate portion at each stage of a process using a photoresist. It is. The photoresist strip method shown below is a diagram showing a photoresist strip method after forming a dual poly gate as an example.

  FIG. 4A shows a step of implanting an N-type impurity element into the NMOS region of the semiconductor substrate using a photoresist pattern. As shown in FIG. 4A, an element isolation film 32 for separating the NMOS region and the PMOS region is formed on the semiconductor substrate 31 in which the NMOS region and the PMOS region are defined.

  Thereafter, a gate oxide film 33 is formed on the semiconductor substrate 31, and a gate polysilicon layer 34 is formed on the gate oxide film 33.

  Subsequently, a photoresist is applied on the gate polysilicon layer 34, and patterning is performed by exposure and development to expose the NMOS region and form a first photoresist pattern 35 that covers the PMOS region.

Next, ion implantation (N ⁺ IMP) of an N-type impurity element is performed using the first photoresist pattern 35, an N-type impurity element is implanted into the gate polysilicon layer 34 in the NMOS region, and N-type doped poly A silicon layer 34A is formed. The N-type impurity element is phosphorus (P) or arsenic (As), and the ion implantation amount is set to a very high level of about 1 × 10 ¹⁶ ions / cm ² and the ion implantation energy is set to a low level.

After ion implantation (N ⁺ IMP) of an N-type impurity element, an N-type doped polysilicon layer 34A is formed on the NMOS region, and a gate polysilicon layer 34 that is not ion-implanted remains on the PMOS region. . Hereinafter, the N-type doped polysilicon layer 34A is abbreviated as “N ⁺ polysilicon layer 34A”.

  FIG. 4B shows the step of stripping the photoresist on the PMOS region. As shown in FIG. 4B, the first photoresist pattern 35 shown in FIG. 4A is stripped. At this time, the strip of the first photoresist pattern 35 is not stripped at a time using a plasma of oxygen plasma or a mixed gas of nitrogen gas and oxygen gas which is usually used, but the first step as follows: The process is divided into three steps in the order of the second step and the third step.

The first step is expressed as a mixed gas of N ₂ and H ₂ (hereinafter referred to as “N ₂ H ₂ gas” or “N ₂ H ₂ ”. The content ratio is 4% H ₂ , 96% N in volume%. ₂ ) and O ₂ mixed gas (by volume, N ₂ H ₂ : O ₂ = 4 to 6: 1) is used at a low temperature (100 to 160 ° C.) using plasma with a source gas as a source gas. . The second step is a gas in which N ₂ H ₂ (4% H ₂ , 96% N ₂ ) gas and O ₂ are mixed (by volume ratio, N ₂ H ₂ : O ₂ = 4 to 6: 1). Is performed at a temperature (200 to 250 ° C.) higher than that in the first step by using plasma with a source gas as a source gas. In the final third step, processing is performed using plasma using N ₂ H ₂ gas alone as a source gas.

As described above, in the first step, plasma (N ₂ H ₂ plasma, O ₂ plasma) using a mixed gas of N ₂ H ₂ gas and O ₂ as a source gas at a low temperature in the range of 100 to 160 ° C. is used. . Here, the N ₂ H ₂ plasma serves as a forming gas for separating an impurity element (eg, arsenic (As)). That is, the arsenic (As) implanted into the first photoresist pattern 35 during ion implantation serves to remove the arsenic (As) from the inside of the first photoresist pattern 35 to the outside. The O ₂ plasma substantially serves to strip the first photoresist pattern 35.

The reason why the first step is performed at a low temperature is that the O ₂ plasma reacts with arsenic (As) to prevent As ₂ O _{3 from} being generated, and the detachment of arsenic (As) by the N ₂ H ₂ plasma occurs. This is to make it easier to do. That is, in the low temperature range of 100 to 160 ° C., than the generation of _As 2 _{O 3} by the _{O 2 plasma,} N 2 _{H 2} plasma by separation of arsenic (As) is generated in advance, followed by _{O 2} plasma The first photoresist pattern 35 is stripped.

A process of removing arsenic (As) remaining in the first photoresist pattern 35 will be described based on a chemical reaction formula. When a mixed gas of N ₂ H ₂ gas and O ₂ gas is introduced into the chamber and a microwave and an RF bias are applied as electric energy, the introduced gas is in a plasma state (by a collision with accelerated electrons). Activated by positive ions, negative ions, electrons, radicals, etc.). Ions, radicals, etc. in the plasma of this N ₂ H ₂ / O ₂ gas are involved in the stripping of the photoresist and the impurity elements. In the first to third steps, a microwave (MW) and an RF bias are used simultaneously to generate plasma. Therefore, during the strip processing in the first to third steps, the N ₂ H ₂ gas becomes N ₂ H ₂ -MW plasma and N ₂ H ₂ -RF bias plasma and plays its role, and O ₂ is O ₂ -MW plasma and O ₂ -RF bias plasma play their roles.

Next, the arsenic (As) elimination process will be described in detail using chemical reaction equations.
Chemical reaction 4:
2As + 6H * → As ₂ H ₆ (gas)
As + O * / O ₃ → As ₂ O ₃ (solid)
As ₂ O ₃ + 12H * → As ₂ H ₆ (gas) + 3H ₂ O (gas)
In the chemical reaction 4, As is arsenic remaining in the first photoresist pattern 35, and H * is a hydrogen radical contained in the N ₂ H ₂ plasma. O * / O ₃ is oxygen radicals / ozone contained in the O ₂ plasma.

According to the chemical reaction 4, As remaining in the first photoresist pattern 35 reacts with H * and is vaporized as As ₂ H ₆ (gas).

In addition, As remaining in the first photoresist pattern 35 reacts with O * and O ₃ contained in the O ₂ plasma to generate solid As ₂ O ₃ . Even if solid As ₂ O ₃ is produced, the produced As ₂ O ₃ reacts with H * to become As ₂ H ₆ (gas) and is vaporized and removed outside the resist layer. Here, 3H ₂ O generated by the reaction of As ₂ O ₃ and H * is removed as a gas outside the resist layer.

Description of the Related Art Since the strip photoresist using only O _2, the reaction of As present inside the photoresist generates O ₂ reacts with solid As ₂ O _3, i.e., by impurity element Oxide film formation occurs prior to stripping of the photoresist pattern with O ₂ . Therefore, the strip of the photoresist pattern by O ₂ is inhibited by the As ₂ O ₃ film.

In the case of the embodiment according to the present invention, when the first step is performed, plasma using a mixed gas of N ₂ H ₂ gas and O ₂ gas as a source gas is used, so that the inside of the first photoresist pattern 35 The arsenic (As) remaining on the surface of the first photoresist pattern 35 can be released to the outside, thereby preventing the formation of a solid As ₂ O ₃ film on the surface of the first photoresist pattern 35. .

Next, a second step is performed following the first step. The second step is a plasma that uses a higher temperature condition (200 to 250 ° C.) than the first step and uses the same mixed gas (a mixed gas of CH ₄ gas and O ₂ gas) as that of the first step as a source gas. Is used. Here, the reason why the temperature condition of the second step is set higher than that of the first step is that the strip speed of the first photoresist pattern 35 can be increased at a high temperature (200 to 250 ° C.).

Therefore, in the first step, the detachment of the impurity element arsenic (As) proceeds preferentially over the strip action of the first photoresist pattern 35. In the second step, since the arsenic (As) has already been removed by the first step, stripping of the first photoresist pattern 35 by O ₂ plasma mainly proceeds.

Finally, the third step is performed following the second step. In this third step, arsenic (As) that may remain in the strip by-product generated in the steps up to the second step is obtained by using plasma using N ₂ H ₂ gas alone as a source gas. Remove. That is, the third step is a process of removing the impurity element remaining in the strip byproduct remaining after the first photoresist pattern 25 is stripped.

  Through the series of first to third steps as described above, the first photoresist pattern 35 is completely removed from the substrate surface without the photoresist remaining.

On the other hand, when phosphorus (P) is present inside the N ⁺ polysilicon layer 34 A, phosphorus (P) is removed by the following chemical reaction 5.
Chemical reaction 5
P + 3H * → PH ₃ (gas)
P + O * / O ₃ → P ₄ O ₆ (solid) or P ₄ O ₁₀ (solid)
P ₄ O ₆ + 24H * → 4PH ₃ (gas) + 6H ₂ O (gas)
P ₄ O ₁₀ + 32H * → 4PH ₃ (gas) + 10H ₂ O (gas)
After stripping the first photoresist pattern 35 through the above-described series of steps, as shown in FIG. 4C, a photoresist is applied again, and a second photoresist pattern 36 is formed by exposure and development. That is, in a state where the N ⁺ polysilicon layer 34A and the gate polysilicon layer 34 coexist, a photoresist is applied to the entire surface and then patterned by exposure and development, thereby exposing the PMOS region and covering the NMOS region. 2 Photoresist pattern 36 is formed.

Then, by using the second photoresist pattern 36 perform ion implantation of P-type impurity element ^(P + IMP), and ion-implanting P-type impurity element to the gate polysilicon layer 34 in the PMOS region, ^{P +} poly A silicon layer 34B is formed. The P-type impurity element is, for example, boron (B), the ion implantation amount is set to a very high level of about 1 × 10 ¹⁶ ions / cm ² , and the ion implantation energy is set to a low level.

  FIG. 4D shows the step of stripping the photoresist over the NMOS region. As shown in FIG. 4D, the second photoresist pattern 36 shown in FIG. 4C is stripped. At this time, the strip of the second photoresist pattern 36 is divided into three steps in the order of the first step to the third step, like the strip of the first photoresist pattern 35.

The first step is a gas in which N ₂ H ₂ (by volume, 4% H ₂ , 96% N ₂ ) gas and O ₂ gas are mixed (by volume, N ₂ H ₂ : O ₂ = 4 to 6: Processing is performed at a low temperature (100 to 160 ° C.) using plasma using 1) as a source gas. The second step is a gas in which N ₂ H ₂ (volume ratio: 4% H ₂ , 96% N ₂ ) gas and O ₂ gas are mixed (volume ratio: N ₂ H ₂ : O ₂ = 4˜ 6: 1) is used as a source gas, and the treatment is performed at a higher temperature (200 to 250 ° C.) than the first step. In the final third step, processing is performed using plasma using N ₂ H ₂ gas alone as a source gas.

As described above, in the first step, plasma (N ₂ H ₂ plasma, O ₂ plasma) using a mixed gas of N ₂ H ₂ gas and O ₂ as a source gas at a low temperature in the range of 100 to 160 ° C. is used. . Here, the N ₂ H ₂ plasma serves as a forming gas for separating the impurity element. That is, the impurity element (for example, boron (B)) implanted into the second photoresist pattern 36 at the time of ion implantation is removed from the inside of the second photoresist pattern 36 to the outside. The O ₂ plasma substantially serves to strip the second photoresist pattern 36.

The reason why the above first step is performed at a low temperature is that the O ₂ plasma reacts with boron (B) to suppress the formation of B ₂ O _{3 and the} boron (B) is detached by the N ₂ H ₂ plasma. This is to make it easier to do. That is, in the low temperature range of 100 to 160 ° C., than the generation of _B 2 _{O 3} by the _{O 2 plasma,} N 2 _{H 2} plasma withdrawal of boron (B) is generated in advance by, followed by _{O 2} plasma The second photoresist pattern 36 is stripped.

The process of removing boron (B) remaining in the second photoresist pattern 36 will be described based on the chemical reaction formula. When a mixed gas of N ₂ H ₂ gas and O ₂ gas is introduced into the chamber and a microwave and an RF bias are simultaneously applied as electrical energy, the introduced gas is in a plasma state due to collision with accelerated electrons. It is activated by (positive ion, negative ion, electron, radical, etc.). Ions, radicals, etc. in the plasma of this N ₂ H ₂ / O ₂ gas are involved in the stripping of the photoresist and the impurity elements. In the first to third steps, a microwave (MW) and an RF bias are used simultaneously to generate plasma. Therefore, during the strip processing in the first to third steps, the N ₂ H ₂ gas becomes N ₂ H ₂ -MW plasma and CH ₄ -RF bias plasma and plays its role, and O ₂ is O _2. It -MW become plasma and _O 2 -RF bias plasma plays its role.

Next, the process of removing boron (B) will be described in detail based on the chemical reaction formula.
Chemical reaction 6:
2B + 6H * → B ₂ H ₆ (gas)
B + O * / O ₃ → B ₂ O ₃ (solid)
B ₂ O ₃ + 12H * → B ₂ H ₆ (gas) + 3H ₂ O (gas)
In the chemical reaction 6, B is boron remaining inside the second photoresist pattern 36, and H * is a hydrogen radical contained in the N ₂ H ₂ plasma. O * / O ₃ is oxygen radical / ozone contained in O ₂ plasma, respectively.

According to the chemical reaction 6, boron (B) remaining in the second photoresist pattern 36 reacts with H * and is vaporized as B ₂ H ₂ (gas).

Further, boron (B) remaining in the second photoresist pattern 36 reacts with O * and O ₃ contained in the O ₂ plasma to become solid B ₂ O ₃ . Solid B ₂ O ₃ is generated, but the generated B ₂ O ₃ reacts with H * to become B ₂ H ₂ (gas), which is vaporized and removed outside the resist layer. Here, 3H ₂ O produced by the reaction of B ₂ O ₃ and H * is removed as a gas outside the resist layer.

Since the conventional technique strips the photoresist using only O ₂ , boron (B) existing inside the photoresist reacts with O ₂ to produce solid B ₂ O ₃ , that is, Oxide film formation due to the impurity element occurs prior to the strip of the photoresist pattern due to O ₂ . Therefore, the strip of the photoresist pattern by O ₂ is inhibited by the B ₂ O ₃ film.

In the embodiment according to the present invention, when the first step is performed, plasma using a mixed gas of N ₂ H ₂ gas and O ₂ gas as a source gas is used. Boron (B) remaining on the surface of the second photoresist pattern 36 can be released to the outside, thereby preventing the formation of a solid B ₂ O ₃ film on the surface of the second photoresist pattern 36. .

Next, a second step is performed following the first step. In this second step, the temperature condition is higher (200 to 250 ° C.) than in the first step, and the same mixed gas (mixed gas of N ₂ H ₂ gas and O ₂ gas) as that in the first step is used as the source gas. Use plasma. Here, the reason why the temperature condition of the second step is set higher than that of the first step is that the strip speed of the second photoresist pattern 36 can be increased at a higher temperature (200 to 250 ° C.).

Accordingly, in the first step, the separation of boron (B) proceeds preferentially over the strip action of the second photoresist pattern 36, and in the second step, boron ( B) is removed. Therefore, the strip of the second photoresist pattern 36 by O ₂ plasma mainly proceeds.

Finally, the third step is performed following the second step. In this third step, boron (B) that may remain in the strip by-product generated in the steps up to the second step is obtained by using plasma using N ₂ H ₂ gas alone as a source gas. Remove. That is, the third step is a process of removing boron (B) remaining in the strip byproduct remaining after the second photoresist pattern 36 is stripped.

  Through the series of first to third steps as described above, the second photoresist pattern 36 is completely removed from the substrate surface without the photoresist remaining.

FIG. 4E shows a stage in which gates are formed in the NMOS region and the PMOS region, respectively. After the second photoresist pattern 36 is stripped by the above-described series of steps, a tungsten silicide layer 37 is formed on the entire surface, and then gate patterning is performed to form an N-type in the NMOS region as shown in FIG. 4E. An N ⁺ poly gate 34C made of a doped polysilicon layer is formed, and a P ⁺ poly gate 34D made of a P-type doped polysilicon layer is formed in the PMOS region.

FIG. 5 is a diagram illustrating a photoresist strip process by a process using plasma of an N ₂ H ₂ / O ₂ mixed gas after boron is ion-implanted under conditions of a low level ion implantation energy and a high ion implantation amount. is there.

As shown in FIG. 5, since microwave and RF bias are simultaneously used to generate plasma, the N ₂ H ₂ gas becomes N ₂ H ₂ -MW plasma and N ₂ H ₂ -RF bias plasma, It plays its role, and O ₂ becomes O ₂ -MW plasma and O ₂ -RF bias plasma and plays its role.

First, in the process of stripping, “B ₂ O ₃ and PR” coexist in the upper layer of the photoresist (PR), and only “PR” exists in the lower layer in contact with the gate polysilicon layer. In the intermediate layer between the upper layer and the lower layer, “BxHyOz and PR” coexist. Here, BxHyOz hydride present in the intermediate layer, in which the hydrogen radicals in the plasma generated reacts with B ₂ O _3, the B ₂ O ₃ like the H * changes in gaseous, gas To be removed.

As noted above, the photoresist layer is present in several forms during the strip process. Of each layer of the photoresist (PR) layer, B ₂ O ₃ and PR of the upper layer are stripped by N ₂ H ₂ -MW plasma and N ₂ H ₂ -RF bias plasma, and BxHyOz and PR of the intermediate layer are Stripped by N ₂ H ₂ -MW plasma and O ₂ -RF bias plasma, the lower layer PR is stripped by O ₂ / N ₂ -MW plasma or O ₂ -MW plasma. Here, B ₂ O ₃ and BxHyOz in each layer are removed as gas in the form of B ₂ H ₆ according to the principle of chemical reaction 6 described above.

Further, the lower layer in which only PR is present is stripped by O ₂ / N ₂ -MW plasma or O ₂ -MW plasma. In this case, since PR is usually a polymer of “C” and “H”, it reacts with O ₂ and is removed as a gas in the form of CO ₂ and H ₂ O.

FIG. 6 is a view showing a state after stripping a photoresist by the method according to the second embodiment of the present invention, and is a photograph showing that there is no photoresist residue. FIG. 6 shows the processing conditions of the first step to the third step when stripping the first photoresist pattern and the second photoresist pattern, the plasma processing chamber pressure: 226.6 Pa (1700 mTorr), and plasma generation. electrical energy: 2000W (MW, RF bias, respectively), _{O 2} flow rate: _4000sccm, N _{2 H} 2 flow rate: performs processing as 800 sccm, a photograph showing the results. From FIG. 6, it can be seen that there is no photoresist residue, unlike the case of the prior art shown in FIG. 1D.

Detailed processing conditions of the first step to the third step are as follows.
The first _{step: 1700mT / 2000W / 4000sccmO 2 /} 800sccmN 2 H 2 / middle
The second _{step: 1700mT / 2000W / 4000sccmO 2 /} 800sccmN 2 H 2 / down
Third _{step: 1700mT / 2000W / 0sccmO 2 /} 800sccmN 2 H 2 / down
In the above steps, “middle” and “down” indicate the temperature of the apparatus to be used, “middle” is about 150 ° C., and “down” is in the range of 200 to 250 ° C.

Since oxide films of impurity elements such as As ₂ O ₃ , P ₄ O ₆ , P ₄ O ₁₀ , and B ₂ O ₃ are water-soluble, before the photoresist strip process (especially before the first step). Then, a pretreatment is performed to remove the oxide film of the impurity element using deionized water at an appropriate temperature. This pretreatment is preferably called “deionized water rinsing, and is preferably performed by a method of immersing an object in deionized water containing ozone (O ₃ ). Here, deionized water containing ozone is The temperature of the solution is preferably in the range of 25 to 80 ° C., and the concentration of ozone is preferably in the range of 0 to 500 ppm. Deionized water containing this ozone can be simply expressed as “H ₂ O”.

The deionized water rinsing step after the ion implantation of the impurity element, when moving the strip device of the photoresist, As ₂ O produced by exposure to the atmosphere (the reaction between oxygen and impurity elements in the air) ₃ , P ₄ O ₆ , P ₄ O ₁₀ , B ₂ O _{3 and the} like are applied to remove oxide films of impurity elements. By this deionized water rinsing step, the surface of the photoresist layer into which the impurity element is ion-implanted is softened, and the oxide film of the impurity element is removed.

  The pretreatment using the deionized water further facilitates subsequent photoresist stripping.

7A to 7D are diagrams showing the results of investigating the influence of the presence or absence of rinsing with ozone-containing deionized water (DI / O ₃ ) on the photoresist strip, and are photographs showing the surface state of the treated surface. is there. The DI / O ₃ treatment was performed separately at room temperature (25 ° C.) and at a high temperature of 80 ° C. FIGS. 7A and 7B are photoresist strip results in the dual poly gate formation process by the beamline ion implantation method, and FIGS. 7C and 7D are photoresist strip results in the dual poly gate formation process by plasma doping. It is. EPR7 [P01] and ENI3 [P02D] shown in FIG. 7C mean that a photoresist strip was performed using O ₂ / N ₂ which is a normal combination.

FIG. 7A shows the surface state after performing ion implantation three times as indicated in the classification column, after DI / O ₃ treatment, after the first PR strip, and after the second PR strip. And the evaluation results of the presence or absence of residues are shown.

From FIG. 7A, it can be seen that no photoresist residue was observed when the DI / O ₃ treatment temperature was high (80 ° C.) or at room temperature (25 ° C.).

FIG. 7B shows the surface state after performing ion implantation three times (1.5 × 10 ¹⁶ ions / cm ² , boron, beam line ion implantation) as indicated in the division column. The photograph after / O ₃ treatment, after PR strip, and after cleaning (CLN) and the evaluation result of the presence or absence of residue are shown.

From Figure 7B, when performing DI / _{O 3} treatment at room temperature (25 ° C.), If you did not DI / _{O 3} treatment, in four steps strip photoresist (FOI using strips, PR strip once) It can be seen that no photoresist residue was observed in either case.

Here, the processing conditions when the strip of photoresist is 4 steps are as follows.
The first _{step: 1700mT / 4000sccmO 2 / 400sccmN 2} H 2 / Middle5 "
The second _{step: 1700mT / 2000W / 4000sccmO 2 /} 400sccmN 2 H 2 / Middle60 "
Third _{step: 1700mT / 2000W / 4000sccmO 2 /} 400sccmN 2 H 2 / Down50 "
Fourth _{Step: 1700mT / 2000W / 0sccmO 2 /} 400sccmN 2 H 2 / Down20 "
As described above, when boron ion implantation was performed by the beam line ion implantation method, it was confirmed that no residue remained after stripping the photoresist irrespective of the DI / O ₃ treatment.

  FIG. 7C shows the strip result of the photoresist with plasma doping (denoted “PLAD”). Plasma doping means a case where boron ion implantation is performed by a plasma doping method.

FIG. 7C shows the result after PLAD (2.5 × 10 ¹⁶ ions / cm ² ), after DI / O ₃ treatment, after the first PR strip, and after the second PR strip, as indicated in the section. The photograph and the evaluation result of the presence or absence of residue are shown.

From FIG. 7C, it can be seen that when the DI / O ₃ treatment was performed at a high temperature of 80 ° C., no photoresist residue was observed. However, when DI / O ₃ treatment was performed at room temperature (25 ° C.), it was recognized that a photoresist remained in part. However, these photoresist residues can be solved by applying the method of the present invention.

FIG. 7D shows a strip result of a photoresist in which boron (B) is ion-implanted by a plasma doping (PLAD) method, which is a case of implantation with an energy of PLAD condition of 3.0 × 10 ¹⁶ ions / cm ² . FIG. 7D shows a photograph after PLAD, after DI / O ₃ treatment, after PR strip, and after cleaning (CLN), and the evaluation result of the presence or absence of residues, as indicated in the category column.

From FIG. 7D, when DI / O ₃ treatment is performed at room temperature (25 ° C.), no photoresist residue is observed, but when DI / O ₃ treatment is omitted, photoresist residue is present. I found out that

According to the results shown in FIGS. 7A to 7D, the DI / O ₃ treatment was effective in removing the photoresist residue. Therefore, in the strip method according to the embodiment of the present invention, by performing the DI / O ₃ treatment, the photoresist can be stripped more effectively without leaving a photoresist residue.

Since the strip method according to the present invention described above uses at least a hydrocarbon-based gas (CH ₄ , C ₂ H ₄ ), even if the ion implantation amount is high, the residue of the photoresist used as an etching barrier All can be stripped without leaving. Therefore, there is an effect that the pattern lifting in the subsequent process can be reduced and the manufacturing yield can be improved.

In addition, the present invention can remove a residue of a photoresist used as an etching barrier by a strip method using plasma using a mixed gas of N ₂ H ₂ and O ₂ as a source gas even in the case of a high ion implantation amount. All can be stripped without leaving. Therefore, there is an effect that the pattern lifting in the subsequent process can be reduced and the manufacturing yield can be improved.

  It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the technical idea according to the present invention. Belongs to a range.

It is sectional drawing which shows the dual poly gate formation method based on the prior art, and has shown the step which implanted the N type impurity element in the NMOS area | region of the semiconductor substrate using the photoresist pattern. It is sectional drawing which shows the dual poly gate formation method based on the prior art, and has shown the step which implanted the P-type impurity element into the PMOS area | region of a semiconductor substrate using a photoresist pattern. It is sectional drawing which shows the dual poly gate formation method based on the prior art, and has shown the step which formed the gate in NMOS area | region and PMOS area | region, respectively. It is a figure which shows the residue after the photoresist removal by a prior art, and is a scanning electron microscope (SEM) photograph. 1 is a cross-sectional view for explaining a photoresist strip method according to a first embodiment of the present invention, and shows a step of implanting an N-type impurity element into an NMOS region of a semiconductor substrate using a photoresist pattern; ing. It is sectional drawing for demonstrating the strip method of the photoresist which concerns on the 1st Embodiment of this invention, and has shown the step which stripped the photoresist on a PMOS area | region. 1 is a cross-sectional view for explaining a photoresist strip method according to a first embodiment of the present invention, showing a step of implanting a P-type impurity element into a PMOS region of a semiconductor substrate using a photoresist pattern; ing. FIG. 5 is a cross-sectional view for explaining the photoresist stripping method according to the first embodiment of the present invention, and shows a stage where the photoresist on the NMOS region is stripped. After boron ions are implanted under conditions of low levels of the ion implantation energy and high ion implantation amount is a diagram showing a strip process of the photoresist by treatment with a plasma of CH 4 _/ O ₂ mixed gas. FIG. 6 is a cross-sectional view for explaining a photoresist stripping method according to a second embodiment of the present invention, and shows a step of implanting an N-type impurity element into an NMOS region of a semiconductor substrate using a photoresist pattern. ing. FIG. 10 is a cross-sectional view for explaining a photoresist stripping method according to a second embodiment of the present invention, and shows a stage in which a photoresist on a PMOS region is stripped. FIG. 7 is a cross-sectional view for explaining a photoresist strip method according to a second embodiment of the present invention, and shows a step of implanting a P-type impurity element into a PMOS region of a semiconductor substrate using a photoresist pattern. ing. FIG. 10 is a cross-sectional view for explaining a photoresist stripping method according to a second embodiment of the present invention, and shows a stage where the photoresist on the NMOS region is stripped. It is sectional drawing for demonstrating the strip method of the photoresist which concerns on the 2nd Embodiment of this invention, and has shown the step which formed the gate in NMOS area | region and PMOS area | region, respectively. After boron ions are implanted under conditions of low levels of the ion implantation energy and high ion implantation amount is a diagram showing a strip process of the photoresist by treatment with a plasma of N _{2 H} 2 _/ O 2 gas mixture. It is a figure which shows the state after performing the strip of a photoresist by the method which concerns on the 2nd Embodiment of this invention, and is a photograph which shows the state in which the residue of a photoresist does not exist. The presence or absence of rinsing with deionized water (DI / O ₃₎ containing ozone is a diagram showing a result of investigating the effect on the strip of photoresist, shows the surface state after three times of ion implantation , After DI / O ₃ treatment, after the first PR strip, after the second PR strip, and the evaluation results of the presence or absence of residue. Shows the results of the presence or absence of rinsing with deionized water (DI / O ₃₎ containing ozone was investigated the effect on the strip of the photoresist, the photoresist in the dual poly gate formation process by the beam-line ion implantation method Strip results are shown. The presence or absence of rinsing with deionized water (DI / O ₃₎ containing ozone is a diagram showing a result of investigating the effect on the strip of photoresist, a strip result of photoresist in a dual poly gate formation process by plasma doping Show. The presence or absence of rinsing with deionized water (DI / O ₃₎ containing ozone is a diagram showing a result of investigating the effect on the strip of photoresist, a strip result of photoresist in a dual poly gate formation process by plasma doping Show.

Explanation of symbols

21 Semiconductor substrate 22 Element isolation film 23 Gate oxide film 24 Gate polysilicon layer 24A N ⁺ polysilicon layer 24B P ⁺ polysilicon layer 25 First photoresist pattern 26 Second photoresist pattern

Claims (40)

Forming a photoresist pattern exposing a portion into which ions are implanted on a predetermined material layer;
Implanting an impurity element into the predetermined material layer using the photoresist pattern as an ion implantation barrier;
Stripping the photoresist pattern by using plasma of a mixed gas containing at least a hydrocarbon-based gas. Stripping the photoresist pattern;
2. The method of stripping a photoresist according to claim 1, wherein the stripping is performed sequentially at different temperatures. Stripping the photoresist pattern comprises:
A first step performed at a first temperature using plasma of a mixed gas of hydrocarbon-based gas and oxygen gas;
A second step performed at a second temperature higher than the first temperature using plasma of a mixed gas of hydrocarbon-based gas and oxygen gas;
The method of stripping a photoresist according to claim 2, further comprising: a third step performed using plasma of a hydrocarbon gas alone.   4. The method of stripping a photoresist according to claim 3, wherein the first temperature is in a range of 100 to 160 [deg.] C. and the second temperature is in a range of 200 to 250 [deg.] C. In the first step to the third step,
The photoresist stripping method according to claim 3, wherein CH ₄ gas or C ₂ H ₄ gas is used as the hydrocarbon-based gas.   The mixing ratio of the mixed gas of the hydrocarbon gas and oxygen gas used in the first step and the second step is hydrocarbon gas: oxygen gas = 4 to 10: 1 in volume ratio. The method of stripping a photoresist according to claim 3. In the first step to the third step,
4. The photoresist stripping method according to claim 3, wherein a microwave and an RF bias are used in combination as electric energy for generating the plasma.   4. The photoresist stripping method according to claim 3, wherein the mixed gas of hydrocarbon gas and oxygen gas further contains nitrogen gas. After the step of ion implanting the impurity element,
The rinsing process using a solution containing at least deionized water is further performed on the predetermined material layer into which the impurity element is ion-implanted. A method for stripping a photoresist according to claim 1.   10. The method of stripping a photoresist according to claim 9, wherein the deionized water contains ozone.   The photoresist stripping method according to claim 10, wherein the rinse treatment is performed under a condition of a temperature of 25 to 80 ° C. of the deionized water.   The photoresist stripping method according to claim 11, wherein the concentration of ozone contained in the deionized water is in the range of 1 to 1000 ppm. The predetermined material layer for ion implantation is
2. The method of stripping a photoresist according to claim 1, wherein the photoresist is a polysilicon layer. The impurity element ion-implanted into the polysilicon layer is
14. The photoresist stripping method according to claim 13, wherein the photoresist stripping method is any one of arsenic, phosphorus and boron. Forming a photoresist pattern exposing a portion into which ions are implanted on a predetermined material layer;
Implanting an impurity element into the predetermined material layer using the photoresist pattern as an ion implantation barrier;
Stripping the photoresist pattern using plasma of a mixed gas containing at least N ₂ H ₂ gas. Stripping the photoresist pattern comprises:
A first step performed at a first temperature using plasma of a mixed gas of N ₂ H ₂ gas and O ₂ gas;
A second step performed at a second temperature higher than the first temperature using plasma of a mixed gas of N ₂ H ₂ gas and O ₂ gas;
The method of stripping a photoresist according to claim 15, further comprising: a third step using a plasma of N ₂ H ₂ gas alone.   The method of stripping a photoresist according to claim 16, wherein the first temperature is in a range of 100 to 160 ° C, and the second temperature is in a range of 200 to 250 ° C. 17. The photo according to claim 16, wherein the N ₂ H ₂ gas used in the first step to the third step contains 4% H ₂ gas and 96% N ₂ gas by volume ratio. How to strip resist. The mixing ratio of the mixed gas of the N ₂ H ₂ gas and O ₂ gas used in the first step and the second step is set to N ₂ H ₂ : O ₂ = 4 to 6: 1 by volume ratio. The method of stripping a photoresist according to claim 16, characterized in that: In the first step to the third step,
17. The photoresist stripping method according to claim 16, wherein a microwave and an RF bias are used in combination as electric energy for generating plasma. After the step of ion implanting the impurity element,
The rinsing process using a solution containing at least deionized water is further performed on the predetermined material layer into which the impurity element is ion-implanted. A method for stripping a photoresist according to claim 1.   The method of stripping a photoresist according to claim 21, wherein the deionized water contains ozone.   23. The photoresist stripping method according to claim 22, wherein the rinsing process is performed at a temperature of the deionized water: 25 to 80C.   24. The photoresist stripping method according to claim 23, wherein the concentration of ozone contained in the deionized water is in the range of 1 to 500 ppm. The predetermined material layer for ion implantation is
16. The method of stripping a photoresist according to claim 15, wherein the method is a polysilicon layer. The impurity element ion-implanted into the polysilicon layer is
26. The method of stripping a photoresist according to claim 25, wherein the photoresist strip is any one of arsenic, phosphorus and boron.   27. The photoresist stripping method according to claim 26, wherein the impurity element is ion-implanted by a beamline ion implantation method or a plasma doping method. Forming a first photoresist pattern exposing a portion of the polysilicon layer on the polysilicon layer;
Implanting a first impurity element into the polysilicon layer using the first photoresist pattern as an ion implantation barrier;
Stripping the first photoresist pattern using a plasma of a mixed gas containing at least N ₂ H ₂ gas;
Forming a second photoresist pattern on the polysilicon layer, exposing a remaining region excluding a region where the first impurity element is ion-implanted;
Ion-implanting a second impurity element into the polysilicon layer using the second photoresist pattern as an ion implantation barrier;
Stripping the second photoresist pattern using a mixed gas plasma containing at least N ₂ H ₂ gas. Stripping the first photoresist pattern and stripping the second photoresist pattern;
A first step performed at a first temperature using plasma of a mixed gas of the N ₂ H ₂ gas and O ₂ gas,
A second step performed at a second temperature higher than the first temperature using a plasma of a mixed gas of the N ₂ H ₂ gas and the O ₂ gas;
29. The method of stripping a photoresist according to claim 28, comprising: a third step using a plasma of N ₂ H ₂ gas alone.   30. The method of stripping a photoresist according to claim 29, wherein the first temperature is in a range of 100 to 160 [deg.] C., and the second temperature is in a range of 200 to 250 [deg.] C. The _N 2 _{H 2} gas is, in volume ratio, the strip method of the photoresist according to claim 29, characterized in that it comprises 4% of _{H 2} gas and 96% of _{N 2} gas. The mixing ratio of the mixed gas of the N ₂ H ₂ and O ₂ gas used in the first step and the second step is N ₂ H ₂ : O ₂ = 4 to 6: 1 by volume ratio. 30. The method of stripping a photoresist according to claim 29. In the first step to the third step,
30. The photoresist stripping method according to claim 29, wherein a microwave and an RF bias are used in combination as electrical energy for generating plasma. After the step of ion-implanting the first impurity element or the step of ion-implanting the second impurity element, the polysilicon layer into which the first impurity element is ion-implanted or the polysilicon into which the second impurity element is ion-implanted, respectively The method for stripping a photoresist according to any one of claims 28 to 33, further comprising: rinsing the layer using a solution containing at least deionized water.   35. The method of stripping a photoresist according to claim 34, wherein the deionized water contains ozone.   36. The photoresist stripping method according to claim 35, wherein the rinsing process is performed under a temperature of the deionized water: 25 to 80C.   37. The photoresist stripping method according to claim 36, wherein the concentration of ozone contained in the deionized water is in the range of 1 to 500 ppm.   29. The method of stripping a photoresist according to claim 28, wherein the first impurity element is N-type and the second impurity element is P-type.   29. The method of stripping a photoresist according to claim 28, wherein the first impurity element is P-type and the second impurity element is N-type. Ion implantation of the first impurity element and the second impurity element;
40. The photoresist stripping method according to claim 38 or 39, wherein the stripping method is performed by a beam line ion implantation method or a plasma doping method.